In the United States, glaucoma is the second leading cause of legal blindness overall and the leading cause of blindness in African-American individuals (Hiller, R and H. A. Kahn, (1975) Am. J. Ophthalmol 80:62 and Kahn, H. A. and H. B. Moorhead (1973) U.S. Public Health Service Publication NIH73-427, 120). Primary open glaucoma (POAG) is the most common form of glaucoma affecting 1-2% of the population over age forty (J. M. Tielsch et al., (1990) Arch Ophthalmol. 108:286). Nearly 12,000 people in the United States are blinded annually by this disorder (H. B. Moorhead (1973) U.S. Public Health Service Publication NIH73-427, 1202-4; J. M. Tielsch et al., (1990) Arch Ophthalmol 108:286 and J. M. Tielsch, in Transactions of the New Orleans Academy of Ophthalmology, Ball, S. F. Franklin R. M., Eds (Kugler, Amsterdam, 1993), pp61-68).
One method of identifying genes involved in multifactorial disorders is to study Mendelian diseases with a similar phenotype. Juvenile open angle glaucoma (JOAG) is a term used to refer to a subset of POAG which has an earlier age of onset and a highly penetrant autosomal dominant mode of inheritance (A. T. Johnson et al., (1993) Ophthalmology 100:524). On clinical examination, patients with juvenile onset open angle glaucoma are identical to patients with later onset disease in that both exhibit elevated intraocular pressure and optic nerve cupping in the presence of a biomicroscopically normal trabecular meshwork.